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Pumps & Cycle Times for 2700l Chift Pist
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Author:  andrew-l [ May 21st, '09, 17:54 ]
Post subject:  Pumps & Cycle Times for 2700l Chift Pist
OK I seem to be going around in circles on this one, so I thought I'd throw it open to everyone for recommendations:

2700 Litre fish tank
4300 Litre growbeds (est 2150 Litres of water)
3000 litre sump
Draining using standpipes, Filled using a timed pump

I had originally planned a 30min fill, 30 min drain. Then realised (am I correct in this?) that that was impossible, as the outflow from the growbeds would equal the inflow - i.e. they would never fill.

So now I'm looking at a fast filll, slow drain, figuring that the faster I fill, the less water is wasted "draining" during the fill period. That has lead me towards two big pumps, running together, to run a 9 min / 51 min cycle:

[*]Two Laguna Powerjet Max Flo 16000 pumps running in parallel for 9 minutes, then gravity drain (standpipe) for 51 minutes.
[*]Loses 480 Litres from the growbeds during fill, so the two pumps deliver a total of 3198 Litres in their 9 minutes.
[*]Total power consumption = 1.19 kWh / day.
[*]Also gives me a little bit of redundancy in the system - and if 1 Pump goes, I can temporarily change the cycle to a 25 min fill, 45 min drain and still survive, albeit a little less efficiently (1.57kWh / day)

I just need a sanity check on this - they seem like huge pumps to me, but I guess it is a largeish system.

Do those numbers stack up? Anyone with a large system happy to tell me those are small pumps :lol:
Author:  fishfodder [ May 21st, '09, 18:50 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
Hi Andrew

Not sure why you think you outflow will equal your inflow if you are using standpipes? Standpipe sit upright in your grow bed and your beds will fill up to the top of the standpipes (recommended to set the top about 1 inch below the top if your media). Once all the beds are full you turn the pump off (timer) and the water slowly drains out of small holes at the bottom of the stand pipe.

Repeat every hour or so. So you need a pump that will pump enough water (2150 litres by your calculations) to fill your beds in about 15 to 20 minutes and you need the holes in the bottom of the standpipes to be big enough to let all the water drain back out in 45 to 50 minutes.
Author:  andrew-l [ May 21st, '09, 18:59 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
Hi FishFodder, thanks for the confirmation on the 15/45 ratio.

fishfodder wrote:
Not sure why you think you outflow will equal your inflow if you are using standpipes? Basically your beds will fill up to the top of the standpipes (recommended to set the top level about 1 inch below the top if your media). Once all the beds are full you turn the pump off (timer) and the water slowly drains out of small holes at the bottom of the stand pipe.


I was thinking that based on a 30 min fill, 30 min drain. To do that the growbed standpipes would need to drain at 2150l in half an hour, and the fill would need to be 2150l in half an hour, so the fill = the drain, so the growbed will never fill. Good job I spotted that before showing off my sparkly new system to anybody else :lol:
Author:  fishfodder [ May 21st, '09, 19:12 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
Cheers, gotcha now. I have two small systems running on timers and I just run the pumps for 30 minutes on and off for 90.

My beds actually fill in about 5 and overflow for 25 while the pump keeps running. Doing it this way mean that the water falling back oxygenates for the 30 minutes that the pump is on. The plants grow just fine even though the bed is actually full-ish for about 40 minutes before they drain down to a lower level.
Author:  andrew-l [ May 21st, '09, 20:41 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
Do you not have problems with DO having the pumps off for 90 mins?

I guess you're not running trout?
Author:  fishfodder [ May 22nd, '09, 06:14 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
Yep that's right no trout. System has been running for 3 months with yabbies (approx 60) and 3 or 4 silver perch with no DO issues.
Author:  andrew-l [ May 22nd, '09, 19:23 ]
Post subject:  Re: Pumps & Cycle Times for 2700l Chift Pist
I'm assuming I need to try and keep to the one-hour turnover cycle to ensure that the trout are getting enough oxygen in the water - particularly when the fish start to get a little large!

Also, as I look at this, it occurs to me to wonder if the gravity overflow from the fishtank will be able to drain fast enough to cope with the inflow from the two pumps?
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